Progressive-cavity pumps (PCPS) are frequently used in the petroleum industry to pump marginal wells. These pumps are typically driven by a motor mounted above the well head through a combination of pulleys and belts. Belt-driven systems present dangers and mechanical problems, such as fast back spin, the difficulty in varying the speed of the pulley system, the high maintenance cost associated with belt failures, and the difficulty in adjusting and or replacing belts and pulleys. Ultimately, because of the frequency of belt repairs and or tightening, workers remove belt guards and do not replace them, rendering the belt driven devices unsafe. Tens of thousands of dollars on a single well may be lost over time due to the operator's inability to make quick pump-speed adjustments to avoid dry pumping and for other problematic situations associated with belt drives.
Several drive head systems have been introduced and designed to address many but not all of the issues described above. Many of the solutions are workable but tend to be costly and therefore are not utilized in marginal oil field situations. There is a need for a pump-driving system that has fewer moving mechanical parts than conventional systems, that is more reliable, safer, and that can be adapted to modern electronic methods of speed control.